Sparse Superposition Coding With Quasi-Orthogonal Projection Matrices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional low density parity check (LDPC) and polar coding techniques used in 5G NR for URLLC message transmission result in lower spectral efficiency due to reduced code rates and modulation orders, which are not designed for short message transmission, leading to tighter error rate targets and diminished coding gains.
Innovation Solution
A transmitter device configured to select a subset of columns from a quasi-orthogonal projection matrix, where each submatrix has orthogonal columns and columns from different submatrices have a correlation of less than or equal to 1/√M, for superposition coding to achieve higher spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LDPC/polar codes are used for URLLC transmission, then reliability is improved, but spectral efficiency deteriorates
Solution Approach 1:
The codebook is segmented into multiple subcodebooks, each containing codewords with specific properties. The transmitter selects appropriate subcodebooks based on channel conditions and message characteristics, enabling adaptive coding that maintains reliability while improving spectral efficiency for short URLLC messages
Solution Approach 2:
The system dynamically changes coding parameters including code rate, modulation order, and codebook selection based on channel quality and URLLC requirements. This allows optimization of the reliability-spectral efficiency tradeoff by adapting parameters to specific transmission scenarios rather than using fixed LDPC/polar code configurations
2Reliability
If code rate is decreased to achieve URLLC reliability, then block error rate is improved, but spectral efficiency deteriorates
Solution Approach 1:
The system employs dynamic code rate adjustment where the code rate is not fixed but adapts based on channel conditions and message length. For short URLLC messages, the system selects code rates optimized for the specific message length and channel quality, preventing the spectral efficiency degradation that occurs with uniformly decreased code rates
Solution Approach 2:
The code rate is changed as a variable parameter rather than a fixed value. The system selects from multiple code rate options based on the specific URLLC transmission requirements, allowing higher code rates to be used when channel conditions permit, thereby maintaining reliability while improving spectral efficiency
3Reliability
If modulation order is decreased for URLLC transmission, then reliability is improved, but spectral efficiency deteriorates
Solution Approach 1:
The modulation order is dynamically adjusted based on channel conditions and URLLC requirements. The system can switch between different modulation schemes (QPSK, 16-QAM, 64-QAM, etc.) depending on the specific transmission scenario, allowing higher modulation orders to be used when channel quality supports them, thus maintaining reliability while improving spectral efficiency
Data Source
AI summary
The invention relates to a transmitter device and a receiver device for efficient transmission of information messages. The transmitter device superposes a selected subset of columns of a projection matrix based on an information message so as to obtain a signal for transmission. The signal is transmitted to the receiver device. The receiver device performs iterative successive interference cancellation on a received signal based on a projection matrix so as to obtain a subset of the columns of the projection matrix and therefrom obtains a recovered information message based on the subset of the columns of the projection matrix. Thereby, it is provided a sparse superposition coding scheme with quasi-orthogonal projection matrix achieving good performance in respect of spectral efficiency. Furthermore, the invention also relates to corresponding methods and a computer program.